BigChief 

I do understand. It's just that bearing races are not case hardened CRS. At least they shouldn't be. They are made from oil hardening tool steel that is specifically alloyed to harden when quenched. This is much stronger than CRS no matter how you process it. It is harder at the surface, so it could be considered case hardened, but it can be ground and reheated to restore maximum hardness to the surface.

Bill Kapaun

You stated case hardening can be RESTORED by heating and quenching.
Case hardening - Wikipedia, the free encyclopedia

spanner48

Having stripped down literally hundreds of wheels, and built a fair few back up, here are some pointers:

• Cups don't wear; they rust [if they haven't had enough grease to keep the water out]

• Bearing balls dull with time. But only the cheapest Chinese-made case-hardened balls actually collapse. The extra cost for Class 25 balls is trivial, and it makes a significant difference to how smoothly the wheel spins. Stainless balls are a waste of money; they wear and go out of round MUCH faster than through-hardened carbon steel ones.

• Most cones are made of relatively soft steel, and case-hardened AFTER grinding the bearing race face. You can tell them, because they are either black all over, or grey [zinc-coated] all over

• High-class cones are through-hardened Oil-Hardening Steel. Because the heating and quenching causes distortions, these cones' race faces are re-machined after hardening. So the race faces are 'raw', precision-ground; not fire-blackened.
– broadly "high-class" means Campag and Shimano Dura-Ace. Wheels Manufacturing replacement cones also look like they are through-hardened
– it's very difficult to get confirmation of the material and heat-treatment for other brands. I suspect that that is because they are only case-hardened.

• The case-hardened layer is only a few microns thick. Once a cone is worn or pitted, it will have gone through that layer, into the softer steel matrix. Trying to regrind the race face will simply expose more soft matrix. The matrix cannot normally be quench-hardened. The cone is scrap.

• For through-hardened cones, it is quit easy to screw the cone onto its axle [with a locking nut]; put it in a bench drill, and regrind the bearing race face with a fine file or stone. Several times, if you are doing really high mileages.

• A "cheapskate" solution: If you feel the wheel is running rough because of pitted cones, mark the end of the axle, and carefully rotate it through 180º before reclamping it to the frame. The wear and pitting will all be on the bottom semicircle of the cone – which is taking the weight of the bike and rider. Turning it 180º will bring the old top semicircle into play. It should be relatively unworn.

fietsbob

I saw a video of the clever Aaron Goss, owner of a Seattle shop,
using 2 drill motors
one spins the cone mounted on an axle,
the other is spinning a tapered grindstone ..

Steel hardening temper goes away if it gets too hot, it must be said..




...

Dave Mayer

Go to your local bike Co-op. At the one I volunteer at, we have a 20 pound bin of all kinds of hub cones. Plus two 50 pound bins of all kinds of front and rear used hubs.

We are also receiving multiple complete bikes as donations - daily. This time of year the rate of inflow is becoming overwhelming. By April, despite how many bikes we prebuild, anything with wheels will fly out the door.

sweeks

I've done this with pedal bearings in a drill (faux lathe) and a Dremel with a green stone. I don't know how well the "re-surfaced" cones wear compared to new ones, but I felt pretty good about them.